Non-toxic, microbicidal cleaning agent containing bioactive glass particles

ABSTRACT

A non-toxic cleaning agent with biocidal and dirt-removing properties, which is used together with a solvent, contains at least one surface-active agent and phosphorus-containing bioactive glass particles. The glass particles preferably release at least 300 μg of alkali metal ions per gram, have an average size of less than 400 μm and contain SiO 2 , CaO, Na 2 O, CaF 2 , B 2 O 3 , K 2 O and/or MgO, as well as P 2 O 5 . These cleaning agents are particularly well suited for cleaning surfaces and textile materials, for use in dishwashing detergents and particularly in medical and food-serving establishments.

BACKGROUND OF THE INVENTION

The invention relates to a nontoxic, fabric-sparing cleaning agent withmicrobicidal action, particularly for textiles, and to its preparationand use.

Cleaning agents are usually compositions containing surface-activeagents capable of solubilizing dirt in a solvent, particularly in anaqueous solvent. Because most dirt contains fats or has fat-likeproperties, it is removed with surface-active agents, particularlysurfactants. In this manner, however, only fat-containing dirt can besolubilized. Other kinds of dirt such as, for example, proteins orprotein-containing dirt, for example blood stains, colored substances,for example coffee or tea, and invisible dirt, particularlymicroorganisms, however, cannot be removed readily in this manner. Forthis reason, cleaning agents usually also contain at least one bleachingagent and/or at least one disinfectant, so that the remaining dirt isremoved, at least in optical terms. After the removal of fatty andpigmented dirt, stains are usually removed oxidatively.

To this end, chlorine-releasing chemicals are often used which, becauseof their high oxidation potential, at the same time also act asdisinfectants. Such oxidation, however, often destroys only the coloredpart of the stain, and the other insoluble substances remaincontaminated with the base substance. Because of its high reactivity,however, chlorine bleach has the drawback of attacking colored textilesand in many cases changing their color or causing discoloration.Moreover, the aggressive chlorine bleach attacks the material to becleaned, particularly textiles, so that after multiple washings theirbasic structure is destroyed, which reduces their strength.

For this reason, attempts have been made in the past to accomplishoxidative bleaching with peracetic acid. Although the acid, per se,exerts a sufficient disinfecting action, its penetration into porousmaterials is low, which particularly in the case of textiles results ininsufficient sterilization. Moreover, like chlorine bleach, peraceticacid, which in cleaning agents is formed from perborates and cleaved-offacyl radicals, exerts an oxidative action although to a lower degree.

This oxidative action, although sufficient to exert the bleaching actionthat destroys colored stains and although gentler to many materials thanare other bleaching agents, does not exert adequate disinfecting actionin all cases. For example, aerobic spore-formers are not removed.Moreover, the use of per acids causes considerable damage to wool.

Finally, peroxide compounds react with proteinaceous dirt causing agingof the protein, particularly in the case of blood stains. Aged proteins,however, are removed more or less incompletely by cleaning agents whensuch agents are allowed to act for the usual length of time.

SUMMARY OF THE INVENTION

Hence, the object of the invention is to provide a cleaning agent whichbesides good cleaning properties exerts a sterilizing action, but initself is not toxic.

Bioactive glasses have been known for a long time and have beendescribed in summary form, for example, by Larry L. Hench and John. K.West in “Biological Applications of Bioactive Glasses”, Life ChemistryReports 1996, vol. 13, pp. 187-241, or in “An Introduction toBioceramics”, L. Hench and J. Wilson, eds., World Scientific, New Jersey(1993). Bioactive glasses, in contrast to conventional glasses, arecharacterized in that they are soluble in an aqueous medium and thatthey form a layer of hydroxyapatite on their surface. Most currentbioactive glasses are prepared either as fusible glass, in which casethey contain much less SiO₂ and much more sodium than normal window orbottle glasses, or they are sol-gel glasses which then, in contrast tofusible glasses, contain a high amount of silicon dioxide and a smallamount of sodium or no sodium at all.

The essential properties of bioactive glass are known to those skilledin the art and have been described, for example, in U.S. Pat. No.5,074,916. Bioactive glass thus differs from conventionallime-sodium-silicate glasses in that it binds to living tissues.

Such bioactive glasses are used, for example, for healing damaged bonesand particularly as synthetic bone transplants. Moreover, they are beingused successfully in the healing of chronic wounds, particularlydiabetic ulcers, as well as pressure sores and bed sores of elderlypatients. For example, John E. Rectenwald, Sean Lee and Lyle L. Moldaweret al. (Infection and Immunity, submitted for publication) were able toshow that in the mouse bioactive glass exerts an inflammatory[sic—“anti-inflammatory” seems to be meant—Translator] action broughtabout by stimulation of interleukin-6 (IL-6) activity and simultaneousinhibition of the inflammation-stimulating cytokines TNF-alpha,IL-1-alpha and IL-10 and of MPO (myeloperoxidase) (see also [Proceedingsof the] 19th Annual Meeting, Surgical Infection Society 1999, Apr.28-May 1, 1999).

Moreover, E. Allen et al. (Department of Microbiology andPeriodontology, Eastman Dental Institute) reported that bioactive glass45-S-5 obtainable from Bioglas®, U,S. Biomaterials, Alachua, Fla. 32615,USA, exhibits antibacterial activity not shown by normal glass beads(window glass).

Such biologically active glasses, however, release considerable amountsof Ca²⁺ ions. Hence, it was to be expected that they would markedlyincrease the water hardness which would lead to increased calciumdeposition and reduced cleaning action, so that they would not besuitable for use in detergents and cleaning agents.

Moreover, it was to be expected that the abrasive action of the glassparticles would cause mechanical damage to materials and, in particular,would cause destruction of textile fabrics.

Surprisingly, we have now found that the afore-defined objective can bereached by means of a cleaning agent containing bioactive glassparticles. Such particles preferably show a solubility higher than 250μg of alkali metal ions per gram of glass, the general expression“alkali metal ions” including alkaline earth metal ions.

Surprisingly, we have now found that a cleaning agent containing suchglass particles not only acts as a biocide against viruses and bacteria,but is also gentle to the skin and to fabrics, causes no allergicreactions and, moreover, is capable of eliminating difficult-to-removedirt such as aged proteins. Surprisingly, the release of alkali metalions, and particularly alkaline earth metal ions such as Ca²⁺ and Mg²⁺,does not reduce the detersive action and also does not increase calciumdeposition. Moreover, the added glass particles do not cause the feareddestruction of or damage to the material to be cleaned, particularlytextile fabrics.

The invention thus relates to a nontoxic cleaning agent with biocidaland dirt-removing properties to be used together with a solvent, saidcleaning agent comprising at least one surface-active agent. Theinvention is characterized in that the cleaning agent contains glassparticles which release more than 250 μg of alkali metal ions oralkaline earth metal ions per gram of glass particles and/or which in anaqueous solution, particularly a physiological aqueous solution, form ahydroxyapatite layer on their surface. Preferably, the glass particlescontained in the cleaning agent of the invention release more than 300μg, and particularly more than 500 μg, of alkali metal ions per gram ofglass particles. Particularly preferred are glass particles releasingmore than 1 mg of alkali metal ions/alkaline earth metal ions per gramof glass.

Such cleaning agents are suitable not only for cleaning and sterilizingsurfaces and surgical instruments, but also for textile materials,particularly in hospitals and clinics as well as in food-servingestablishments.

The cleaning agent of the invention is also particularly well suited asa dishwashing agent, particularly for dishwashing machines.

The bioactive glass contained in the cleaning agents of the invention ispreferably a conventional bioactive glass, well known to those skilledin the art. Such glasses usually contain a maximum of 60 wt. % of SiO₂,a high amount of Na₂O and CaO as well as phosphorus, the latter in ahigh molar ratio of calcium to phosphorus, said ratio in most, but notnecessarily all, cases having a value of about five. When such bioactiveglasses come in contact with water or with a body fluid, they give riseto special reactions, namely the sodium and calcium ions of the glassare exchanged for H⁺ ions from the solution by a cation-exchangereaction. As a result, a silanol groups-presenting surface is formed onwhich sodium hydroxide and calcium hydroxide accumulate. The increase inhydroxyl ion concentration at the glass surface now brings about afurther reaction with the silicon network giving rise to additionalsilanol groups which can also lie more deeply in the glass.

Because of the high, alkaline pH in the interstitial glass space, amixed hydroxyapatite phase of CaO and P₂O₆ is formed which crystallizeson the SiO₂ surface and in biological materials binds tomucopolysaccharides, collagens and glycoproteins.

The molar ratio of calcium to phosphorus is preferably >2 andparticularly >3 and preferably <30 and particularly <20, a ratio of <10being particularly preferred.

Particularly preferred are cleaning agents with bioactive glassparticles containing SiO₂, CaO, Na₂O, P₂O₆, CaF₂, B₂O₃, K₂O and/or MgO.If the cleaning agent contains bioactive particles of fusible glass,these particles preferably contain 40-60 wt. % of SiO₂, 10-30 wt. % ofCaO, 10-35 wt. % of Na₂O, 2-8 wt. % of P₂O₅, 0-25 wt. % of CaF₂, 0-10wt. % of B₂O₃, 0-8 wt. % of K₂O and/or 0-5 wt. % of MgO, based on thetotal weight of the glass. If the bioactive glass is a fusible glass,then the upper limit of the silicon dioxide it contains is 60 wt. % andpreferably 55 wt. %, an upper limit of 50 wt. % being particularlypreferred. The sodium oxide content is preferably higher than 15 wt. %and particularly higher than 18 wt. %. A sodium oxide content of ≧20 wt.% is particularly preferred.

If the bioactive glass contained in the cleaning agent of the inventionhas been produced by the sol-gel process, its silicon dioxide contentcan be appreciably higher than in fusible glasses and its sodium oxidecontent can be nil. Bioactive glasses made by the sol-gel processpreferably contain 40 to 90 wt % of SiO₂, 4 to 45 wt. % of CaO, 0 to 10wt. % of Na₂O, 2 to 16 wt. % of P₂O₅, 0 to 25 wt. % of CaF₂, 0 to 4 wt.% of B₂O₃, 0 to 8 wt. % of K₂O and/or 0 to 5 wt. % of MgO.

The phosphorus oxide content of both previously described kinds ofbioactive glass is preferably at least 2 wt. % and particularly at least4 wt. %.

The microbicidal glass particles present in the cleaning agents of theinvention have an average particle size d₅₀ of ≦400 μm and particularly≦250 μm, particle sizes of ≦100 μm being particularly preferred. Inprinciple, a higher surface-to-weight or surface-to-volume ratio resultsin a higher sterilizing biocidal activity than that of larger particles.Unusually high biocidal activity is attained, for example, withparticles having an average size of <50 μm, particularly with particlesof <20 μm or <10 μm, particle sizes of <5 μm being particularlypreferred.

We have found, however, that in the practical range glass particle of 2to 60 μm, particularly of 2 to 50 μm and preferably of 2 to 20 μm bytheir abrasive action promote the mechanical removal of dirt particlesthus markedly enhancing the cleaning action.

Moreover, the cleaning agent of the invention exerts aprotein-degrading, namely solubilizing action. This action manifestsitself also with aged, i.e. denatured proteins.

The desired sterilizing, germ-killing action can be attained with thecleaning agent of the invention alone without adding other additives,particularly without additives releasing Ag⁺, Cu⁺, Cu²⁺ and/or Zn⁺.Nevertheless, such additives may be desirable for the purpose ofachieving synergistic effects. The biocidal activity of the cleaningagent of the invention can be enhanced synergistically by addition ofother sterilizing and germ-killing agents or agents exerting antibioticaction.

Although it was to be expected that the addition according to theinvention of glass particles to a cleaning agent would, particularly forcalcium-containing water, require the addition of a large amount ofcomplexing agents to prevent lime and dirt deposition on the cleanedmaterial, we have found, surprisingly, that the addition of delimingagents such as complexing agents, for example polyphosphates, can bemarkedly reduced or entirely eliminated without any feared lime depositsbeing formed. Rather, any existing lime deposits are removed by theabrasive action of the glass particles.

In a preferred embodiment of the invention, the cleaning agent of theinvention contains the glass particles in an amount of up to 20 wt %, orup to 10 wt %, preferably up to 7 wt % and particularly up to 5 wt %,dry basis. The minimum amount is 0.01 wt % and particularly 0.1 wt %, anamount of at least 0.5 wt % or 1 wt % being particularly preferred. Theusual amount is 1-4 wt %.

The invention also relates to a process for making such cleaning agents,said process being characterized in that surface-active agents,particularly a mixture of different surface-active agents, particularlysurfactants, is mixed with the afore-defined glass particles and themixture is optionally diluted with a solvent.

The invention also relates to the use of such cleaning agents forcleaning surfaces, surgical material and beverage bottles and as or indishwashing agents. Another special use involves the cleaning oftextiles particularly for medical establishments, hospital personnel andfood-serving establishments.

What is claimed is:
 1. A non-toxic cleaning agent with biocidal anddirt-removing properties for cleaning conjointly with a solvent, saidnon-toxic cleaning agent comprising at least one surface-active agentand glass particles, wherein said glass particles consist of aphosphorous-containing bioactive glass.
 2. The cleaning agent as definedin claim 1, wherein said glass particles release at least 300 μg of saidalkali metal ions per gram of said glass particles.
 3. The cleaningagent as defined in claim 1, wherein said glass particles have anaverage size of less than 400 μm.
 4. The cleaning agent as defined inclaim 1, wherein said glass particles have an average size of less than100 μm.
 5. The cleaning agent as defined in claim 1, wherein said atleast one surface-active agent is a surfactant compound.
 6. The cleaningagent as defined in claim 1, wherein said phosphorus-containingbioactive glass contains from 40 to 60 percent by weight of SiO₂, from10 to 30 percent by weight of CaO, from 10 to 35 percent by weight ofNa₂O, 2 to 8 percent by weight of P₂O₅, up to 25 percent by weight CaF₂,up to 10 percent by weight of B₂O₃, up to 8 percent by weight of K₂O andup to 5% by weight of MgO.
 7. The cleaning agent as defined in claim 1,containing from 1 to 7 percent by weight of said glass particlesconsisting of said phosphorous-containing bioactive glass.
 8. A methodof preparing a non-toxic cleaning agent, said non-toxic cleaning agentcomprising at least one surface-active agent and phosphorous-containingactive glass particles, said method comprising adding saidphosphorous-containing bioactive glass particles to said at least onesurface-active agent, wherein said phosphorous-containing bioactiveglass particles release at least 250 μg of said alkali metal ions pergram of said phosphorous-containing bioactive glass particles.
 9. Amethod of cleaning at least one object or at least one surface, saidmethod comprising the steps of: a) providing a non-toxic cleaning agentcomprising at least one surface-active agent and glass particles, saidglass particles consisting of a phosphorus-containing bioactive glass;and b) treating at least one object or at least one surface with saidnon-toxic cleaning agent conjointly with a solvent.
 10. The method asdefined in claim 9, wherein said at least one object is made of atextile material.
 11. The method as defined in claim 9, wherein said atleast one object is a dish.
 12. The method as defined in claim 9,wherein said at least one surface is in a medical establishment or in afood-serving establishment.
 13. The method as defined in claim 9,wherein said glass particles have an average size of less than 400 μmand release at least 300 μg of said alkali metal ions per gram of saidglass particles in an aqueous solution.
 14. The method as defined inclaim 9, wherein said non-toxic cleaning agent contains from 1 to 7percent by weight of said glass particles consisting of saidphosphorous-containing bioactive glass.
 15. The method as defined inclaim 9, wherein said phosphorus-containing bioactive glass containsfrom 40 to 60 percent by weight of SiO₂, from 10 to 30 percent by weightof CaO, from 10 to 35 percent by weight of Na₂O, 2 to 8 percent byweight of P₂O₅, up to 25 percent by weight CaF₂, up to 10 percent byweight of B₂O₃, up to 8 percent by weight of K₂O and up to 5% by weightof MgO.